Chilling video from the Kenya mall massacre shows the heavily armed attackers chatting on cell phones as they methodically gunned down terrified victims.

Surveillance camera footage, obtained by CNN and aired Thursday, showed the calm scene as shoppers walked through the Westgate Mall in Nairobi moments before the al-Shabaab terrorists invaded it on Sept. 21.

Warning: Graphic footage

The edited video shows terrified shoppers running for their lives past up-scale stores in the mall and cowering behind counters.

One gunmen is seen firing at a man on the floor. After the terrorist leaves, the victim tries to get up from the blood-stained floor but another gunman returns to finish him off.

The video also shows the gunmen pausing at one point to bow down in an Islamic prayer.

Police suspect the footage showing the men talking on cell phones indicates they were getting instructions from leaders outside the mall.

Four terrorists are shown: two inside the mall and two others making their way through the parking lot, where they opened fire on shoppers hiding under cars. Police initially said as many as 15 terrorist took part in the raid that killed at least 67 people.

The footage also shows two women hostages, one of them wounded, being rounded up by a gunman.